Recording paper



Patented Mar. 22, 1932 UNITED STATES PATENT OFFICE IfiBANCIS G. MOREH OUSE, F GB 'EEHWICH CONNECTICUT, .ASSIGNOB T0 RADIO COB- PORATION 0] AMERICA, A CORPORATION OF DELAWARE RECORDING PAPER R0 Drawing.

located remotely from a transmitting station of any desired type. More particularly, the invention is directed to a suitable ty e of recording paper for recording the plcture messages as they are received from the remotely located transmitting point. 7

Of course, by the term picturesas used throughout the specification, I mean any particular form of message which may be-recorded to produce a representation which will affect the optical senses and convey information, and the term may include, views, photographs, financial statements, newspapers, magazine articles, advertisements, fashion plates, motion picture films, checks, documents, finger prints, and the like.

By my copending application, Serial No. 324,421, filed on December 7, 1928, jointly with Richard Howland Ranger, I have disclosed a system wherein it is possible to use heat for producing a record on a wax treated paper, and a system wherein the original application of heat by means of a process of selective absorption produces what has been termed a latent image on the paper. This latent image is, for example, a picture made up of a suitable aggregation of lines, dots, areas, etc., which are ink-absorptive against a background which is completely inkrepellent, or, in other words, the latent image portion of the record surface is absorptive to ink and the wax treated paper is repellant to ink.

As disclosed by the above named copending application, the latent image is produced by means of a jet of hot air projected against the paper, by a hot stylus made to touch the paper at different points thereon in accordance with received signals, or by any other heat producing means of sufiicient heat intensity to melt the Wax at points intended to represent the message. It is obvious that the more completely the local absorption of the wax coating into the paper support is attained, the more satisfactory will the finished record be, from the points of view of pho- Application filed December 18, 1929. Serial No. 415,141.

tographic contract and the general neatness and accuracy of recording. If the degree of wax-absorption is inadequate, it is found that the smallest dots and the finest lines of the latent image, are not faithfully brought out in good contrast by the inking process but tend to appear faint or are entirely absent from the finished record.

Therefore, as a primary object of the present invention, I have attempted to improve upon the process of recording by the use of a hot air jet, a hot stylus, or heat produced from a concentrated light source projected against the recording surface so as to melt due to the heat application,-

the wax coating thereon and cause the same to'be absorbed by the paper.

As a further purpose and object of my invention, I desire to produce a recording paper for use in the recording of pictures or the like which is more readily fusible than papers heretofore known and used, and which will require a lower degree of heat for producing any recording action. so that there may be a consequent longer life of the recording unit. I also desire to provide a recording sheet upon which greater recording speeds are possible, and a sheet which more closely approaches the speed of photographic recording sheets than has heretofore been known.

As a further object of my present invention, I desire to provide by means of the more complete selective absorption, a finished record which is a more faithful reproduction of the orig nal, even to the finest dots and lines,

than has heretofore been possible through the use of wax recording films or the like, and a record in which the degree of contrast between the finished picture and the background is materiallv improved.

Other objects and advantages, of course,

will become apparent and readily suggest liquid form (as, for example, from an equeous colloidal emulsion or suspension) to one side of the paper sheet by surface dipping. After the wax coating thus placed upon one surface of the paper was allowed to dry, it was desirable to polish the wax film with a soft hair brush, so as to smooth the surface and produce a polish thereon, and also to avoid some of the granulated effects due to 710 the unevenness of initial distribution of the wax film, which would be objectionable.

However, under such conditions, it was observed that upon the application of heat to the recording surface, the wax film thereon was not melted at the low temperatures which were .to be expected from considerations of the known melting point of the wax. Due to the fact that foreign substances of higher melting point were placed with the wax in order to maintain the wax liquid in an emulsion state, the wax was not completely fused and therefore not absorbed by the paper stock sufficiently to perm t sharp contrast when ink was applied thereto at portions where the wax had been supposedly completely absorbed by the paper.

Therefore, according to my present invention, have sought to develop a method and means whereby the objectionable features of this nature may be overcome, and as a means by which I accomplish the desired results, I have added what I have herein termed a coagulant as an additional coating on the paper, and have coated the paper in the following manner: to one surface of a sheet of absorbent paper, I have applied by surface dipping a coagulant, to be hereinafter described, and have then permitted this coagulant to dry upon the sheet. After the coagulant has been dried upon the sheet, I then apply a thin film of wax in the same manner.

as was previously done in theprior art, and which was d sclosed in my copending application, reference to which has been made above. I then allow this wax film to dry upon the paper, and I then polish the paper with a soft hair brush in the manner above described in connection with the paper having the coating only of wax.

Most of the commercial wax emuls ons which are obtainable are apparently in the form of an aqueous suspension having a qualitative composition somewhat as follows: (a) wax (such as parafiin) (b) soaps (as emulsi fying agents) (c) preservatives, stabilizers, etc. (d) an aqueous vehicle. The addition of the coagulant to the coating upon the recording surface is intended to function or serve to increase the fusibility of the wax film. Such coagulants as may be used may be either of the organic or the inorganic type. Where coagulants of the organic type are used, they should be such organic compounds as dissolve in water to form an acid solution, and may consist, for example, of tartaric acid,

acetic acid, phthalic acid, oxalic acid, benzoic acid, citric acid, and other organic compounds of like nature. Where it is desired to use inorganic substances as coagulants, these inorganic compounds should be such that they dissolve in water to form an acid solution, and may consist, for example, of nickel sulphate, copper sulphate, ferric chloride, strontium chloride, cadmium sulphate, maganese nitrate, lead nitrate, lead acetate, aluminum sulphate, chromium sulphate, aluminum nitrate, and other inorganic compounds of like nature.

While experimentation has indicated what is apparently the true chemical theory of operation of the coagulant with respect to the wax emulsion so as to produce reactions such that make the entire composition more readily fusible and permit a lower degree of heat to be used in recording, and a consequent longer life of recording unit, I wish it to be distinctly understood that any theory which I may herein express is not'to be regarded as limiting my invention, but is disclosed simply for the purpose of more clearly ex plaining the nature thereof in the manner in which I at present understand it. This theory may be expressed somewhat as follows: As the wax emulsion is applied to the paper coated with the coagulant as above stated,

the process of application to the paper partially dissolves the coagulant, which is believed to interact with the wax emulsion, and the following altered composition apparently results by virtue of the acidity of the dissolved coagulant: First, the wax (such as the parafiin) apparently remains unchanged; second, the free fatty acids corresponding to the soaps used as emulsifying agents are produced; third, the preservatives stabilizers, etc; remain unchanged and fourth, the aqueous vehicles remains unchanged, but, of course, drys out, as stated above, to form the dry wax film on the paper. It is thus observed that the soaps are the only ingredients that undergo any change due to the presence of the coagulant, and experimentation indicates that the film resulting from the application to the paper of the mixture of the wax, the free fatty acids, the preservatives, stabilizers, and the aqueous Vehicle, is more readily fusible than the film resulting from the mixture of wax, soaps, preservatives,

- stabilizers and the aqueous vehicle, since the application of heat represents a more complete attainment of the condition of selective absorption than has heretofore been obtainable, and, after inking, the record exhibits improved faithfulness of reproduction and better contrast.

Many modifications and changes in the present invention will at once suggest them selves and become apparent to those skilled in the art to which the invention relates, and while I have hereinabove illustrated by way of example several of the man substances which I may use as coagulants, believe that I am entitled to use any and all of such substances as fall fairly within the spirit and scope of the invention as defined by the here inafter appended claims.

Having now described my invention, what I claim and desired to secure by Letters Patent is the following: i

1. A heat sensitive recording sheet provided with a coagulant and a wax film on the surface thereof.

2. A heat sensitive recording sheet havin a coagulant coating on the surface thereo and a waxy emulsion superposed upon the coagulant.

3. A heat sensitive recording sheet having an inorganic coagulant coating the surface thereof, and a waxy emulsion superposed upon the coagulant.

4:. The process of preparing papers for heat sensitive recording which consists in coating the paper stock with a coagulant, and, after drying, again coating the paper provided with a coagulant on the surface thereof with a waxy heat sensitive emulsion.

5. The process of preparing a paper stock for heat sensitive recording which consists in coating one surface of the paper stock with a coagulant, drying the coated paper, coating the dried paper stock provided with the coa ulant with a waxy emulsion, and in again drying the entire sheet.

6. heat sensitive recording sheet having an organic coagulant coating the surface thereof, and a waxy emulsion superposed upon the said coa ulant.

rRANcis G. MOREHOUSE; 

